Collabora Office CUMIPMT_ADD: Accumulate loan interest over inclusive periods
Calculate CUMIPMT_ADD interest with matched periodic units, payment timing, signed cash flows and the analysis add-in’s integer argument contract.
Verification status: See the evidence and test scope described in this guide. How formula examples are checked
Quick answer: for a 1,200-unit loan at 1% per period, repaid in twelve equal end-of-period installments, =CUMIPMT_ADD(0.01;12;1200;3;6;0) independently gives approximately −34.5627414444. This is interest for payments 3, 4, 5 and 6, not the entire payment amount.
Syntax and required inputs
=CUMIPMT_ADD(Rate; NPer; PV; StartPeriod; EndPeriod; Type)
All six arguments are required. Rate is the rate per payment period. NPer is the total number of payments, and PV is the positive initial principal. StartPeriod and EndPeriod are inclusive, numbered from 1. Type 0 means payments at each period’s end; Type 1 means payments at the beginning. Official CUMIPMT_ADD help.
Keep Rate and NPer in the same time unit. A nominal annual rate of 12% compounded monthly corresponds to 0.12/12 = 0.01 per month. An effective annual rate needs a different conversion; do not automatically divide every annual rate by twelve.
The source requires Rate > 0, PV > 0, StartPeriod ≥ 1 and StartPeriod ≤ EndPeriod ≤ NPer. Type must become 0 or 1 after the add-in’s integer conversion. This function models a level-payment, fully amortizing schedule with zero final balance; it has no separate balloon-value argument.
Worked example: interest during periods 3–6
Enter:
| Cell | Meaning | Value |
|---|---|---|
| B2 | Periodic rate | 0.01 |
| B3 | Total periods | 12 |
| B4 | Initial principal | 1200 |
| B5 | First included payment | 3 |
| B6 | Last included payment | 6 |
| B7 | Payment timing | 0 |
Use =CUMIPMT_ADD(B2;B3;B4;B5;B6;B7). The independent result is −34.5627414444397.
A separate balance schedule gives the level payment as −PV×r/[1−(1+r)^(−N)], approximately −106.6185464140. At each end-of-period payment, interest is the negative opening balance times r; principal is payment minus interest; the remaining balance decreases by that principal outflow. Summing the interest components for rows 3 through 6 gives the stated result.
The negative sign denotes cash paid out against a positive initial principal. If a report wants a positive expense magnitude, display the negative of the result deliberately; do not change PV to a negative value, which this evaluator rejects.
Advanced use: reconcile interest with principal
The same interval’s CUMPRINC_ADD result is approximately −391.9114442116. Adding the two components gives −426.4741856560, exactly four level payments in the independent model, apart from rounding.
For all twelve end-of-period payments, cumulative interest is approximately −79.4225569681, while cumulative principal is −1200. This provides a useful schedule check: interest plus principal should reconcile with the payments over the same inclusive interval and timing convention.
Keep full precision in the schedule. Rounding every period’s interest and principal to currency cents can create a small residual that differs from the unrounded formula model. Fees, irregular payments and contractual rounding adjustments are outside this six-argument calculation.
Beginning-of-period timing is a different schedule
With Type 1 the first payment occurs immediately, so its interest component is 0. Thus =CUMIPMT_ADD(0.01;12;1200;1;1;1) predicts zero, whereas the Type 0 first-period interest is −12.
The beginning-of-period level payment is the end-of-period payment divided by 1.01, approximately −105.5629172416. For periods 3–6, Type 1 independently gives interest −34.2205360836. It is not obtained by merely shifting the Type 0 interval labels; the payment amount and outstanding balances also change.
Integer conversion and distinction from CUMIPMT
The analysis add-in binds NPer, both endpoints and Type as signed 32-bit integers. The caller conversion uses GetInt32, which approximately truncates finite fractional values toward zero before the financial evaluator sees them.
Consequently, =CUMIPMT_ADD(0.01;12.9;1200;3.9;6.9;0.9) follows the source path for NPer 12, endpoints 3 and 6, and Type 0. This is a compatibility distinction, not a recommendation to supply fractional periods or timing flags.
Unsuffixed CUMIPMT retains a floating-point total period count and validates its payment-type value differently. The suffix therefore matters. The help’s general Excel 2003 compatibility wording is not an independently tested guarantee for every input or file format.
Rate 0, StartPeriod 0, a reversed interval, an endpoint beyond NPer, nonpositive PV or an invalid converted Type causes the add-in evaluator to throw IllegalArgumentException. This guide records the source condition without inventing a native displayed error string.
Product scope, compatibility and evidence
This guide covers the new Collabora Office desktop for Linux, using the Flathub source tag coda-26.04.4.3-1 and commit 81339d176148d0d5c81ff05d82540f58f8aaa117. The official desktop release notes and Linux package manifest identify that product/build. The package manifest is a dated observation from October 18, 2026, rather than an installed-binary check.
The 26.04 function help and exact evaluator source were inspected on October 18, 2026. Expected examples were independently calculated; no Collabora application was run. Expected scalar results were derived from the documented contracts, inspected source and independent calculations; native output formatting and error localization have not been tested. Classic, Online/CODE, other operating systems and file-format round trips require their own checks.
Availability here is established from the function-specific help and the mapped package source. Related functions may have different arguments or boundary rules. The first Collabora release introducing this function is not established by the reviewed sources. No cited retirement or deprecation notice was found. Unknown introduction dates do not imply that the function is deprecated. File-format round trips require separate verification.
Related functions
- CUMPRINC_ADD: reconcile the principal component for the same interval
- CUMIPMT: compare the unsuffixed argument contract
- EFFECT_ADD: distinguish nominal and effective annual rates